I did not consider the water powered pump very seriously as they didn't
sound like they could handle much water. I am dealing with some
unknowns here. A water powered one might be perfectly adequate, but
then again maybe not. I'd rather not lie awake rainy nights worrying
about it. I know the battery powered pump is not 100% perfect, but it
seemed to be a better choice. Unless I want to take the belt and
suspenders approach and make a water powered pump the THIRD pump.
Hmmmm.

I have installed two water powered pumps and they have both been shoddy
little POSs that I was concerned would fail, making the problem even worse.
Maybe there are good ones out there, but I haven't seen them.
The one battery backup I put in was much more substantial.